[chimera-dev] Finding central Axis of Strand

Hello, I am developing my own extension to find the central axis of a strand. I am using the nitrogen atoms of a strand to estimate this line, but I have not been able to estimate the end of the strand so that it follows the ribbon. I have attached an image below that displays this error. Currently I am using the next nitrogen atom on the loop to extend my line, but I was wondering how Chimera does this with the ribbon. As you can see in the image, one end of the strand is very accurate, but the side with the arrow head has some problems. Thanks for your help. -- Devin Haslam Old Dominion University, Norfolk, Virginia